On a webpage that was updated this morning to share Apple's most recent environmental report, a Frequently Asked Questions section makes a mention of MacOS



From MacRumors:

When discussing power consumption of products, MacOS is listed alongside tvOS, iOS, and watchOS.To model customer use, we measure the power consumed by a product while it is running in a simulated scenario. Daily usage patterns are specific to each product and are a mixture of actual and modeled customer use data. Years of use, which are based on first owners, are assumed to be four years for MacOS and tvOS devices and three years for iOS and watchOS devices.A mention of "MacOS" was also found buried Library files in OS X 10.11.4 in late March, but the file, "FUFlightViewController_macOS.nib," has been present in the Mac operating system since August of 2015, a month before the public launch of OS X El Capitan.

If Apple does make the switch from "OS X" to "MacOS," it is not clear if the company will stick with naming each iteration after California landmarks, a tradition that started with OS X Mavericks in 2013. Prior to that date, Mac updates were named after large cats, but since then, we've seen OS X Mavericks, OS X Yosemite, and OS X El Capitan. With tvOS, watchOS, and iOS, operating system upgrades follow a number-based naming scheme, with the current versions being tvOS 9.2, watchOS 2.2, and iOS 9.3.1.

  Apple Refers to OS X as MacOS in Environmental Webpage Update